Nidal Hasan was sentenced to death for killing 13 people at Fort Hood, Texas. / AP

by Tom Vanden Brook, USA TODAY

by Tom Vanden Brook, USA TODAY

WASHINGTON - The Pentagon ordered the military to be on the lookout for troubled troops and civilians after the November 2009 massacre at Fort Hood, Texas, which killed 13 people.

One of the recommendations of a special commission was intended to alert authorities about troubled troops and military civilian employees like the former sailor-turned-contractor suspected of fatally shooting 12 people at the Navy Yard in Washington.

The suspect in Monday's shootings, Aaron Alexis, had been discharged from the Navy for misconduct. He had also been cited for firearms violations in the past. He died Monday.

The recommendations went into effect after Maj. Nidal Hasan killed 13 and wounded 32 in a rampage at Fort Hood. Hasan was convicted last month and given the death penalty.

Among the changes recommended by the Pentagon commission that investigated the Fort Hood shootings:

â?¢ Increased awareness paid to those with emotional problems and to intervene when "they appear at risk."

â?¢ Expanded sharing of information about suspicious activities among local, state and federal law enforcement officials. Alexis had negative marks while serving in the Navy and had a citation for a firearms violation after he served. It's unclear whether his background raised any flags.

â?¢ Lessons learned from the initial response to the Fort Hood shootings were to be incorporated among military law enforcement officials as well as training for "active shooter awareness."

The report, "Protecting the Force: Lessons from Fort Hood," noted that "this event shows us, too, there are no safe havens - for soldiers, sailors, airmen and Marines, their co-workers and their families."

The Army has instituted changes as well, said Laurie Dette, a spokeswoman. They include enhanced training for active shooter incidents, security forces carrying long rifles and enhanced reporting of suspicious activity, Dette said.

One Pentagon office, the Defense Personnel and Security Research Center (PERSEREC), specializes in researching potential internal threats in the military.